1 Field of the Invention
The invention relates to air bag restraint systems for automotive vehicles and, more particularly, relates to an apparatus and method for controlling whether an air bag is activated during vehicular operation according to the weight of the vehicle occupant.
2 Description of the Prior Art
Air bags in automotive vehicles serve to protect vehicle occupants in the event of a vehicle impact by supplementing the occupant restraint provided by seat belts. When air bags were first introduced into automobiles, the air bags were typically only employed on the driver's side across from the front seat. However, dual front-seat air bags are now commonplace and, by 1999, all new vehicles will be equipped with dual air bags.
While air bags have proven to save lives and prevent serious injuries in many situations, the explosive nature of their deployment does involve risk to vehicle occupants. In particular, the force of an inflating air bag is known to be potentially deadly to infants in rear-facing seats and may also severely injure older children, causing face and brain injuries. The risk of injury to adults by an inflating air bag is present, albeit less than the risk to children. On balance, the risk of injury to adults from an air bag is generally considered to be less than the risk of injury from vehicular impact, while the reverse may be true for children and infants.
Several approaches have been developed to reduce the risk of air bag-related injuries to children and adults. One general approach involves tailoring the air bag inflation rate and fill pressure to accommodate for different sizes and positions of vehicle occupants. One such system is available from AirBelt Systems LLC under the trade designation IntelliFlow.TM. Care Bag.TM.. Another general approach has been to deactivate the air bag when the vehicle seat is either unoccupied or occupied by a rear-facing infant seat, such as described in U.S. Pat. No. 5,570,903, issued to Meister et al. and assigned on its face to Echlin, Inc. of Branford, Connecticut.
Meister et al. teach one embodiment in which an array of occupancy sensors is disposed within the passenger-side seat that comprise a plurality of linear Hall effect sensors. Each sensor is positioned beneath a corresponding magnet and provides an electrical output signal that varies as a linear function of proximity to the magnet. The signal may then be analyzed to determine the position and weight of an occupant, if any, and to time the air bag deployment accordingly.
The sensor system of Meister et al. deactivates the air-bag system only if the predetermined vehicle seat position is either (a) unoccupied, as determined by the weight sensor array, or (b) occupied by a rear-facing infant seat, as determined by an optical sensor system. The system of '903 does not deactivate when a small child occupies the predetermined vehicle seat unless the child is in a rear-facing infant seat. Conversely, the sensor system of '903 may be prematurely deactivated if the seat occupant momentarily arises out of the seat, such as during vehicular impact, given the almost instantaneous nature with which its electronic sensors respond to compression and decompression of the seat by an occupant.
There remains a need for an apparatus and a method for discriminating when an air bag should be activated based upon the weight of the vehicle occupant, i.e., allowing the air bag to remain disabled if the vehicle occupant weights less than a predetermined amount. Additionally, the apparatus and method should employ safeguards against the improper deactivation of the air bag upon a momentary shift in weight by the vehicle occupant. The apparatus and method must be reliable and should be relatively inexpensive and easily installed.